Elimination of testicular regression by 12-hr temporal relationship of serotonergic and dopaminergic activity in Indian Palm Squirrel,Funambulus pennanti

Abstract

Specific temporal relationship (12-hr) of serotonin and dopamine activity was induced by precursor drugs (5-HTP and L-DOPA) in Indian Palm Squirrel Funambulus pennanti during testicular regression phase. This treatment established breeding condition unlike control, which experienced complete atrophy of testes and accessory sex organs. It is obvious that seasonal testicular regression of Indian Palm Squirrel can be eliminated by 12 hr relation of 5-HTP and L-DOPA, which is not a pharmacological effect but actually is an alteration of seasonality in this annually breeding subtropical mammal. It may be concluded that specific phase relation (12-hr) between circadian serotonergic and dopaminergic oscillations may induce breeding condition in regressing gonad of Indian Palm Squirrel during post-reproductive phase of annual gonadal cycle. It is also suggested that inspite of the different environmental factors (photoperiod, humidity etc.) used by different species to time their annual reproduction, basic regulatory mechanism of seasonality appears to be the same, i.e., temporal synergism of neurotransmitter activity.

Temporal phase relation of circadian neural oscillations as the basis of testicular maturation in mice: A test of a coincidence model

“…This suggests a stimulatory effect of this relationship on the rate of reproduction/fertility. However, testis growth/volume and spermatogenic activity in 12-h mice (unlike the plasma testosterone level and the sperm index) were not signifi cantly different from the controls, in contrast to previous reports on various other species (Wilson and Meier 1989;Chaturvedi and Bhatt 1990;Chaturvedi and Prasad 1991;Jaiwal and Chaturvedi 1991;Phillips and Chaturvedi 1995;. By the end of the study, the control mice attained nearly full gonadal development; but, a stimulatory effect of the 12-h phase relation on all the parameters of testicular function was not evident, in spite of a signifi cantly increased degree of gonadal activity as compared with the controls.…”

“…Both testes were excised and weighed. The testicular volume was calculated using Bissonett's formula 4/3πab 2 (a = ½ the long axis; b = ½ the short axis) (Jaiwal and Chaturvedi 1991;Chaturvedi et al 1993). …”

Suppression of annual testicular development in Indian Palm Squirrel,Funambulus pennanti by 8 hr temporal relationship of serotonin and dopamine precursor drugs

“…Second study in this series reported that L-DOPA injected 12 hr after 5-HTP may even induce redevelopment of gonad up to full breeding condition when given in sexually quiescent phase of annual cycle (Jaiwal and Chaturvedi, 1991). Next experiment in this series (present study) was designed to study the effect of L-DOPA injected 8 hr after 5-HTP (8 hr relationship, gonadoinhibitory) in this species during breeding phase.…”

Temporal Phase Relation of Circadian Neural Oscillations Alters RFamide-Related Peptide-3 and Testicular Function in the Mouse

“…Twenty-four days after the last injection, when the mice were 58 days old, they were anesthetized and treated as described for study I. The length and width of the left testis was measured in situ with dial calipers, and the testicular volume was calculated using Bissonett’s formula (4/3) π ab 2 ( a = 1/2 of the long axis; b = 1/2 of the short axis) [8,9]. Histological sections of the testis were viewed under a microscope (Axioskop 2 Plus; Carl Zeiss, Oberkochen, Germany), and images were captured with a digital camera.…”

“…On the other hand, if these drugs are injected 8 h apart (8- hour relation), this may lead to gonadal suppression/non-breeding conditions, while other relations (0, 4, 16 and 20 h) have been found to be ineffective. In the Indian palm squirrel, Funambulus pennantii , the 12-hour phase relation of serotonergic and dopaminergic oscillations not only extends the breeding season, but may also eliminate annual reproductive regression [8]. On the other hand, in this subtropical mammalian species, an 8-hour phase relation stimulates non-breeding conditions out of season [9].…”